Hard disk drive incorporating rotating magnetic disks is commonly used for storing data in the magnetic media formed on the disk surfaces, and a movable head are generally used to read data from and write date into tracks on the disk surfaces.
A conventional magnetic head for a slider typically includes a read portion for reading data from the disk, and a write portion for writing data into the disk. Presently, magnetoresistive (MR) sensor is used as a kind of popular read sensor because of its better capability to read data from disk surface at a greater track and linear densities than traditional film inductive slider. Thus, the read portion of the magnetic head is generally formed by a MR read head, such as Current Perpendicular to Plane (CPP), Current In Plane (CIP), tunnel magnetoresistive (TMR), giant magnetoresistive (GMR), or anisotropic magnetoresistive (AMR) read heads.
For example, FIG. 1 shows a conventional magnetic head 200 including a CPP-TMR read head 210 for reading data from the disk and a write head 220 for writing data into the disk. The magnetic head 200 includes a substrate body 201, an air bearing surface (ABS) 202 and a bottom surface (not shown) opposite to the ABS 202, a trailing edge 203 and a leading edge (not shown) opposite each other. The ABS 202 is processed so as to an appropriate flying height. And the read head 210 and the write head 220 are provided on the trailing edge 203.
As shown in FIG. 2a, the read head 210 includes a substrate layer 214, two shielding layers 211, 212, and a MR element (not labeled) sandwiched therebetween. As illustrated, the MR element is a standard and normal MR element and includes a pinning layer (or an antiferromagnetic (AFM) layer) 236, two synthetic pinned layers 231, 234, a tunnel barrier layer 235, a free layer 237, and a cap layer 232. The read head 210 further includes a pair of hard magnet layers 238 placed at two sides of the MR element on the buffer layer 216 for longitudinally biasing the magnetization of the free layer 237, and an insulating layer 239 for separating and isolating the hard magnet layer 238 from the free layer 237 and the other layers of the MR element.
Referring to FIG. 2a again, concretely, the pair of hard magnet layers 238 has a magnetic direction, indicated by arrow 258, the magnetic direction 258 orients generally parallel to the ABS 202 (shown in FIG. 1). The pinned layer 231 has a pinned direction 254 for preventing from rotation in the presence of applied magnetic fields in the desired range of interest. Desired by manufacturer and the customers, the pinned direction 254 of the pinned layer 231 should be oriented perpendicular to the ABS 202 to achieve the best function, which is called normal pinned direction or standard pinned direction. The free layer 237 contains a ferromagnetic substance and has a magnetization direction 256 that changes in responds to an external magnetic field. Also desired, it's the best that the magnetization direction 256 of the free layer 237 orients parallel to the ABS 15 in the absence of an applied external magnetic field, under this case the magnetization direction is called normal magnetization direction or standard magnetization direction. In other words, ideally, the normal pinned direction 254 of the pinned layer 231 is perpendicular to the normal magnetization direction 256 of the free layer 237.
However, in the practical application of a magnetic head product, the actual pinned direction 254′ of the pinned layer 231 always has an offset to the normal pinned direction 254 for certain factors, and the actual magnetization 256′ of the free layer 237 also has an offset to the normal magnetization direction 256, as shown in FIG. 2b, for example. As illustrated, the actual pinned direction 254′ tilts from the normal pinned direction 254 at an angle of θ1, and the actual magnetization direction 256′ tilts from the actual pinned direction 254′ at an angle of θ2. By all appearances, the above-mentioned tilt angles are not desired since it will bring unstable performance. However, there is still no solution for the manufacturers to accurately measure out the actual tilt angles θ1, θ2 yet. Thus it's hard for the technical persons to test the instability of the pinned layer and free layer with being ignorant of their tilt angles. Accordingly, a remedy and an improvement for the drawbacks resulted by the tilt angles could not be implemented. Worse still, the magnetic head may be abandoned due to the severe tilt angle.
Hence, it is desired to provide a measuring method of a magnetic head to measure out the above-mentioned tilt angles, so as to overcome the drawbacks mentioned-above.